Automatic firearm feed mechanism



Feb. 24, 1948. A. M. ALEXANDER 2,436,370

AUTOMATIC FIREARM FE ED MECHANISM Filed July 24, 1942 2 Sheets-Sheet l t N u art/um All: art M. Alexander A. M. ALEXANDER 2,436,370 AUTOMATIC FIREARM FEED MECHANISM Feb. 24, 1948,

Patented Feb. 24.1948

our TED STATES PATENT o F F ICE AU'L'QMATIG EI REARM FEED'MEGH NISM Albert M, Alexander, Havre de Grace-Md.

Applioationaluly 24, 1942, Serial No. 452,156

aclaims. (01. 89- 33).

("(Jrranted under the act of March. 3, 1883; as amended April 30, 1928; 37.0. 0. Go. 751')! The invention described herein maybe man-ufactured and used by orfor" the Government for governmental purposes, without the payment to me of any royalty thereon This invention relates to automatic firearms, and is concerned particularly with means for operating a cartridge feed mechanism in re.- sponse to firing of. rounds from the gun.

As shown hereafter, the invention is applied to a gun and feed. mech ni m o x stin Wi t- The gun is one in which the breechbolt is unlocked by gas pressure taken from the. propulsive gas in the gun barrel as a cartridge is fired, after which the breechbolt is moved rearwardly against a sp g b co i ed a t on of a pre su nd cartridge setback. Rearward breechbolt movement ejects a fired case. while forward breechbolt movement under spring urging loads a new round into the gun chamber. Power feed of belted ammunition is necessary, since the weight and number of rounds of ammunition is variable and considerable. The teed mechanism formerly used consisted of a star-wheel system to which belted ammunition was fed, and from which consecutive rounds were passed to the gun, the star-whee s being spring urged to carry ammunition to the gun. Spring force on the star-wheels was secured by cocking the spring in response to gun recoil as the gun moved in recoil after each .Shot was fired. In this connection, the gun was mounted for movement in recoil, against a spring, while the feed mechanism was stationary. Frequently the movementof the gun in recoil tell below the normal maximum, due to lack of synchronism between the gun movements and the cyclic hrs rate of the gun, and consequently the feed mesh:-

anism spring. would not be cooked consistently. its force would become spent after firing a tow rounds, and the gun wouldiaii to iunction du to lack of ammunition.

An object of this invention is to proyide posir tive means to cook an automatic gun teed mocha an sm spring synchronously with the cycli rate cf gunfire.

.A f e ob ec is to .do thi by a a ope a ed mechanism. w

A further object is to do this on a gun which is movable in recoil relative to a stationary mount while the feed mechanism is relatively immobile.

In general, the invention consists in securing to a gas operated piston on the gun, which must reciprocate'for every round fired, a cam engageable with a spring cocking cam follower on the stationary feed mechanism, the gun being movable relative to the feed mechanism.

The invention will be understood from reading: the detailed description below in connection with the drawings, which:

Figure 1 is an oblique side view of the gun and feed mechanism assembly, showing its. mounting,

Figure 2 is a broken oblique view of part of the gun and of the feed mechanism, and- Fi'gure 3 is a fragmentary oblique view of a portion of the gun, partly in section, showing the gas port and-gas operatedpiston.

Fig. 4 is a, fragmentary detail of the gas-open ated' pawl and closely-associated parts.

Referring first to Figure 1, the comprisesa barrel in and a receiver H, the barrel having a slidable bushing t2 thereon which is securedto a rigid mounting member 13 which latter member comprises a portion of the gunmou-nt. Ahead of the bushing 1-2 and its associated nut M is a compression spring 45 abutting at its forward end against a flange 46 secured to the gun barrel. The receiver H is provided with lips 11 slidablymounted in a block t8, the block being rigid and forming a part of the gun mount. It will thus be seen that the gun is bodily movable in-recoi'l with respect to the members and I8, the spring l5 serving to move the gun into battery position afterit' has been displaced rearwardly due to recoil.

The breech mechanism of the gun contained within the receiver H is automatic and its details do not form a specific part of the invention. However, the breech mechanism in the type of gun shown is operated by a combination of gas and setback. The gas operating arrangement is shown in part in Figure 3 wherein the barrel it) is ported intermediate its length as at 28, the port communicating with a hollow in a barrel clamp 21', said hollow communicating with a gas cylinder '22 within which a piston 23 is axially movable. -Whe n a cartridge is' fired and the bullet passes the port 28, a small amount or the propellant gas is" passed to the cylinder 22 through dril-lings 24 the cylinder assembly, which gas drives the piston 23 rearwardly against a pring 215 abutting on a piston guide 26 rigid with the gun receiver as sholwnin Figures-2 and 4 A bridge piece 2 integral with the rear portion of the piston 23 operates rods 28 which pass into the receiver and serve to unlockthe breechbolt and to initiate rearwardmovement of the breech! bolt. As the bolt is unlocked, cartridges setback resulting from the ignition .of the propellant charge drives the bolt rearward to eject the spent cartridge. Upon forward movement of the bolt a new cartridge is picked up from a feed slot 29 in the top of the receiver and is chambered in the barrel.

The type of gun shown does not have an integrated cartridge feed mechanism but a separate mechanism is indicated at 36. This mechanism in general is not new. It is arranged, however, so that the gun as a whole may reciprocate axially with respect to itthat is, the mechanism is slidably mounted on the top of the gun and is constrained against axial movement with the gun by a brace 3| secured at its ends to the mounting block l8 as at 32 and to the mechanism 7 -36 as at 33.

The mechanism 30 comprises a cylindrical container 35 having an opening 36 through which cartridges are fed on a suitable belt (not shown) from which the cartridges are picked up on starwheels 38 and 39 mounted upon a common shaft 46 borne in the cylinder 35 and as the star-wheels rotate, by means presently to be described, the cartridges are carried around the cylinder and are delivered to the cartridge guide '29 in the gun receiver ll.

Torque is applied to the star-wheels by means of a spiral spring 42 mounted in a drum 43 on the star-wheel 38, the outer end of the spring engaging a notch in the drum as at 44 and the inner end of the spring engaging one of several notches 45 on a shaft 46 coaxial with the shaft 40. It will be seen that as the star-wheels rotate in a clockwise direction as shown in Fig. 2, the spring 42 will unwind. The mechanism about to be described serves to wind the spring during gun operation to maintain substantially constant feed torque on the star-wheels 38.

The shaft 46 extends to the right and carries on it a ratchet wheel 48 engaged by a spring pressed pawl 49 mounted in the forward end of the feed mechanism 36, A forward prolongation of the shaft 46 carries a hexagonal projection 56 which may be turned by means of a wrench to wind the spring 42 to obtain-the required initial torque on the star-wheel assembly. The pawl 49 prevents the unwinding of the spring after it has been set up.

The vrear face of an extension of the wheel 48 carrying the ratchet teeth is provided with radial serrations 52, engaged by complementary radial serrations on a sleeve 54- loosely fitted on the shaft 46. Said sleeve has a segment of a gear 55 formed on its circumference, the gear teeth being engaged by a vertically reciprocable rack member 56 supported in suitable bearings, not shown, in the case 35 of the feed mechanism. A spring 51 normally urges the member 56 downwardly. When the member 56 is raised the sleeve 54 in turned in a clockwise direction and the synchronous with the cyclic rate of movement of the gun bolt. Furthermore, the distance through which the entire gun reciprocated in recoil varied to such a degree that positive operation of the feed mechanism was not secured. Occasionally during gun operation the cam did not raise the feed mechanism-cocking member 56 and would fail to wind the feed mechanism spring originallywound to apply, say 50 ft. lbs. of torque to the feed mechanism, the torque would grad- .ually drop off during gun operation until it reached such a low value that the feed mechanism would fail to deliver cartridges to the gun. This situation was particularly obnoxious when long belts of ammunition were being used. After failure to operate due to the lack of feed, it would be necessary for a gunner to Wind the spring 42 manually by application of a wrench to the projection 50. If the gun were installed in a submerged location in aircraft, which was frequently the case, the guncould not be restored to firing condition during flight,

The specific improvement in the feed mechanism which I have contributed to the art is the mounting of a feed mechanism operating cam on the gas operated recoil piston 23. This cam is shown at 64 and comprises a. block having a ramp 65 at its rearward end below which is disposed a roller 66, The forward end of the block is pivotally mounted in an adapter 68 rigidly secured to the saddle member 21 on the rear end of the gas operated piston 23. In connection with the cam 64, the roller 66 thereof, after the cam is driven rearwardly, rolls upon a surface 59 on a platform 69a formed on the feed mechanism so sleeve turns the member 48 through engagement of the radial serrations 52, thus Wing the spring 42 a small amount. After such winding, the spring 51 forces the member 56 downwardly turning the sleeve 54 in a counter-clockwise direction while the serrations 52 slip past one another. The sleeve 54 is urged in a forward direction for se l-ration engagement by'a light helical spring 59 around the shaft 46.

- In the past, this feed mechanism was operated by a cam rigid with the gas operated piston support 26 which cam engaged a roller 60 at the bottom of the member 56 for the purpose of raising the member 56 as the entire gun moved rearwardly in recoil. This cam was unsatisfac- .tory due to the fact that the cyclic rate of reciprocation of the entire gun was not necessarily that the downward pressure on the member 56, exerted by the spring 51, is taken directly against the platform of the feed mechanism structure rather than being imparted to the gas operated piston 23. After the gun is fired the piston 23 has a positive rearward movement of slightly less than 1 and piston movement is necessarily synchronous with the rate of gun fire since piston movement controls the rate of gun fire. Thus, the cam 64 is moved rearwardly to raise the cocking mechanism positively at every firing of the gun regardless of the rate and distance of reciprocation of the gun in the rigid mounts l3 and l 8.

-In general, the relatively simple change which I have made in the gun and feed mechanism, including the elements 64 through 68 provides, in an automatic weapon, a gas operated cartridge feed system and furthermore permits of the combination of a gun mounted for bodily movement and recoil along with a stationary feed mechanism. This combination is of considerable value since the cyclic rate of fire of the gun may be increased where the extra mass of the feed mechanism is not forced to reciprocate with the gun. Furthermore, by maintaining constant torque on the feed mechanism, ammunition belts contain ing many more rounds of ammunition maybe used with the gun than could be used heretofore.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

What I claim is:

1. In an automatic firearm of the type mounted recoil, and having a receiver and a cartridge feed,

mechanism fixed to the gun mount in the region of the receiver, the improvement comprising a gas piston carried by the firearm and in communication with the bore gases of the firearm for rearward motion thereby, means for returning the gas piston to forward position, and means carried by the gas piston constructed and arranged to operate the feed mechanism on reciprocation of the firearm, whereby the feed mechanism is indexed completely on each reciprocation of the firearm regardless of the extent of recoil of the firearm, said feed-mechanism including means for storing energy to operate the feed mechanism, a reciprocal element for imparting energy to said storing means by reciprocation, a spring urging said element in one direction, and a platform contacting said element to limit movement thereof in said one direction; said means carried by said gas piston including a cam pivoted at one of its ends to the gas piston, the other and reduced end of said cam resting upon said. platform out of engagement with said reciprocable element when the piston is in forward position, said cam entering between said platform and said reciprocable element during recoil of said piston whereby said cam moves said element in reciprocation away from said platform, said cam being withdrawn from between said platform and said reciprocable element by counter recoil movement of said piston to permit said spring to return said element in reciprocation into contact with said platform.

2.- In an automatic firearm of the type mounted for limited reciprocation in recoil and counter recoil, and having a receiver and a cartridge feed mechanism fixed to the gun mount in the region of the receiver, the improvement comprising a gas piston carried by the firearm and in communication with the bore gases of the firearm for rearward motion thereby, means for returning the gas piston to forward position, and means carried by the gas piston constructed and arranged to operate the feed mechanism on reciprocation of the firearm, whereby the feed mechanism is indexed completely on each reciprocation of the firearm regardless of the extent of recoil of the firearm, said feed mechanism including means for storing energy to operate the feed mechanism, a vertically reciprocable element for imparting energy to said storing means by reciprocation, a spring urging said element down- 6 wardly, a platform beneath said reciprocable ele-* ment contacting said element to limit downward movement thereof, and a roller on the lower end of said reciprocable element at the point of contact between said reciprocable element and said platform, said platform having a downwardly inclined portion positioned forwardly of said point of contact; said means carried by said gas piston including a cam pivoted to the gas piston near the forward end of the cam, a platform engaging roller on the rear end of said cam resting upon said inclined portion of said platform with the rear end of the cam out of engagement with said reciprocable element when the piston is in forward position, said cam rolling between said platform and said reciprocable element during recoil of said piston to move said element upwardly in reciprocation, said cam being withdrawn from between said platform and said reciprocable element by counter recoil movement of said piston to permit said spring to return said element in reciprocation into contact with said platform.

. ALBERT M. ALEXANDER.

REFERENCES GITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,332 Farquhar et al. 1914 317,161 Maxim May 5, 1885 454,403 Odkolek June 16, 1891 1,063.882 Jones June 3, 1913 1,140,715 Purcell May 25, 1915 1,290,852 Sturgeon Jan. 7, 1919 1,290,854 Sturgeon Jan. 7, 1919 1,381,016 Reising June 7, 1921 1,401 667 Brown Dec. 27, 1921 1,730,269 Dame Oct, 1, 1929 2,146,185 Holek Feb. 7, 1939 2,291,867 Birkight Aug. 4, 1942 2,357,127 North Aug. 29, 1944 2,366,395 Hall Jan. 2, 1945 2,377,828 Trotter et al. June 5, 1945 2,378,191 Corte June 12, 1945 FOREIGN PATENTS Number Country Date 22,274 France Dec. 28, 1920 (Addition to No. 503,079) 355,767 Great Britain Published 1931 197,276 Germany Apr. 23, 1908 

